Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of the common general knowledge in the field.
Known espresso machine control both the pressure and dose of water delivered in producing a shot of espresso coffee. It will be appreciated that the pressure is typically set to between nine and ten bar. The dose is typically about 30 mL, and is delivered in between twenty to forty seconds.
A pre-infusion stage has been used to wet the coffee grinds to allow expansion within a filter basket, thereby assisting in trapping fine grinds and restricting water from tracking though the filter. To enable wetting without forcing water though the coffee grinds, the water delivered in this pre-infusion stage usually has a pressure between one to five bar.
There is a need for an efficient method and apparatus for providing a dose having a regulated pressure and volume. There is also a need to provide an efficient method and apparatus for enabling an espresso machine water pumps to deliver a controlled low pressure pre-infusion.
Espresso machines are also known to have steam wands. The steam wand omits steam that can be used, for example, to heat and froth milk. In some machines, the steam output is regulated by a valve such as a needle valve. A needle valve provides a variable steam output but must be rotated numerous times when proceeding from a closed state to a fully opened state.
Accordingly, there is also a need for a steam output control that provides greater ease of use than a needle valve.